[Bug tree-optimization/103464] [12 Regression] ICE on valid code at -O1 (with -ftree-vrp and ulimit -s 512) on x86_64-linux-gnu: Segmentation fault since r12-5522-g661c02e54ea72fb5

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103464

--- Comment #14 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #13)
> Note that r12-5522-g661c02e54ea72fb5 doubled the stack use of the frame by
> adding another int_range_max local to range_of_phi.
> 
> First of all in the rev we should have used intersect_, not union_, and if we
> consider that we can simply treat it like single_arg (which we even set),
> and thus elide equiv_range completely by using arg_range which is already
> computed?  If there are only equivalences to the PHI def then the PHI must
> be undefined (but I wonder how such PHI is even possible - did you have a
> testcase for this?)

So we run into this visiting single arg PHIs where surprisingly we already
have registered an equivalence.  Special-casing single-arg PHIs might make
sense anyway.